1.What is the Rötzer method
The Rötzer method (German: Natürliche Empfängnisregelung, NER) is a fertility awareness-based method belonging to the sympto-thermal family. It combines daily basal body temperature (BBT) readings with observation of cervical mucus, optionally supplemented by self-examination of the cervix.
In the literature it is regarded as the first fully sympto-thermal method: its author was the first to make the evaluation of the temperature rise dependent on the mucus peak. As a result, the end of the fertile phase is confirmed by two independent indicators – a principle known as the double check.[1, 2]
The method is used to avoid pregnancy, to achieve it (by identifying the days with the highest probability of conception) and to monitor cycle health – e.g. to recognise anovulatory cycles or a short luteal phase.
Temperature
Confirms ovulation after the fact – a rise caused by progesterone.
Cervical mucus
Announces approaching ovulation and marks its peak.
Cervix
An additional sign – changes in position, firmness and opening.
2.History and author
Prof. Dr. med. Josef Rötzer (1920–2010) was an Austrian physician and a graduate of the University of Vienna. He researched fertility awareness for almost three decades – assisted by his wife Margareta and, from 1974, also by his daughter Elisabeth.
- Born on 21 March in Vienna.
- Doctorate in medicine at the University of Vienna; works at the institute of pathological anatomy.
- Public health officer in Vöcklabruck (Upper Austria). After coming across leaflets on the basal thermometer at the Vienna Spring Fair, he begins systematic observations with his wife – she notices that temperature changes are accompanied by changes in mucus.
- The book Kinderzahl und Liebesehe – the first description of a sympto-thermal method.[3]
- Paper in Archiv für Gynäkologie on “extended” basal temperature measurement with mucus observation.[1]
- Speaks at a Human Life Foundation meeting in Washington; lectures in the USA, Australia, New Zealand and Asia.
- Results of ten years of effectiveness research published in The Linacre Quarterly.[2]
- Final formulation of the method’s rules.
- Founds the Institute for Natural Conception Regulation (INER). Branches are established in Poland, Croatia, Italy and Paraguay, among others.
- Awarded the title of professor by the President of Austria; in 2002 the Order of St. Gregory the Great.
- Dies on 4 October. INER continues his work.
His handbook Natürliche Empfängnisregelung has gone through more than 30 editions and has been translated into many languages, including Polish (Naturalna regulacja poczęć. Droga współodpowiedzialności).[4]
3.Cycle physiology – the basis of the method
Pre-ovulatory phase: oestrogen and mucus
The maturing ovarian follicle secretes increasing amounts of oestradiol. Under its influence the cervical crypts produce mucus that becomes increasingly clear, stretchy and slippery. E. Odeblad described biophysical mucus types: the oestrogenic L and S types and the P type appearing just before ovulation. In S-type mucus sperm move quickly and can survive for several days.[11]
Ovulation and the mucus peak
The last day of best-quality mucus – the mucus peak – usually falls very close to ovulation. It can, however, only be identified retrospectively, when the mucus quality deteriorates on the following day.
Post-ovulatory phase: progesterone and temperature
After ovulation the corpus luteum secretes progesterone, which (1) turns the mucus into the thick G type that is impenetrable to sperm and forms the cervical plug, and (2) has a thermogenic effect – raising the resting temperature by a few tenths of a degree (classically about 0.3 °C).[12, 11] The temperature stays at the higher level until the next menstruation.
The fertile window
Wilcox et al. showed that conception is possible in a window of about 6 days ending on the day of ovulation – sperm survive up to about 5 days, the egg for less than a day.[10] This explains why the rules at the start of the cycle must precede ovulation with a margin, while the temperature – which confirms ovulation only after the fact – is used to identify the end of the fertile phase.
The key idea of the method: mucus announces ovulation, temperature confirms it. The start of the fertile phase is set by signs and calculation rules, its end by agreement of both indicators.
4.Observations and charting
Taking the temperature
- Every day in the morning, right after waking, before getting up or any activity, after several hours of uninterrupted sleep.
- Always by the same route within a cycle: vaginally or rectally (about 5 minutes) or orally (longer).
- A thermometer accurate to 0.05–0.1 °C.
- Disturbed readings – fever, alcohol, short sleep, stress, travel, a different measuring time – are recorded in brackets and ignored when setting the baseline.
Observing mucus
Mucus is observed throughout the day – both the sensation at the vaginal opening (dry, wet, slippery) and its appearance. In the evening the most fertile sign of the day is recorded. Mucus is divided into three categories: no mucus, poor-quality mucus and good-quality mucus. On the chart a day without mucus is marked Ø, and a day with mucus with the letter S and a small code for the mucus type above it – just like on a paper chart and in the app:
| Chart notation | Description |
|---|---|
| None · no sign of fertility | |
| Ø | None |
| Poor quality · before the peak: start of the fertile phase; after the peak: deterioration confirming the peak | |
| b S | Whitish, usually thick |
| m S | Cloudy |
| kr S | Creamy |
| kl S | Sticky |
| gr S | Lumpy |
| ż S | Yellow, usually lumpy |
| żt S | Yellowish, often stretchy |
| Good quality · high fertility; the last day in this category before deterioration is the peak day | |
| Bj S | Raw egg white |
| szk S | Glassy |
| pł S | Liquid |
| mś S | Wet and slippery |
Cervix
An optional observation. In the infertile phase the cervix is low, firm and closed; before ovulation it rises, softens and opens. The first change is a sign of fertility.
Other records
The chart also records bleeding (menstruation, spotting), intercourse and factors that may disturb the observations. Seminal fluid may mask the mucus picture on the following day.
5.End of the fertile phase – post-ovulatory infertility
Post-ovulatory infertility is absolute: Prof. Rötzer’s data record no conceptions from intercourse in this phase.[2, 4] It is determined in the following sequence:
- Identify the mucus peak – the last day of best-quality mucus before it deteriorates or disappears (not necessarily the day of the largest amount).
- After the peak, mark the first higher temperature – higher than the six preceding lower readings.
- Count back the 6 lower temperatures, skipping disturbed (bracketed) readings.
- Draw the baseline through the highest of them.
- Mark the following readings: 3 consecutive temperatures above the baseline are needed, with the third at least 0.2 °C higher.
- Infertility begins on the evening of the day of the third higher temperature – provided all three higher readings fall after the mucus peak.
Special situations
Slow rise
If the third higher temperature is not 0.2 °C above the baseline, a fourth higher reading is awaited – it only needs to be above the baseline.
Temperature drop
One of the higher readings may fall to or below the baseline – it is then not counted and the evaluation moves on by one day.
Rise before the peak
In some women the temperature rises before the mucus peak. Higher readings are counted only after the peak – whichever indicator is confirmed later decides.
Disturbed and missing readings
A bracketed reading changes neither the counting nor the height of the baseline. A single missing value among the six lower ones does not prevent evaluation.
Without a clear temperature rise post-ovulatory infertility cannot be determined – the cycle may be anovulatory. Higher temperatures persisting much longer than a typical luteal phase are a sign of possible pregnancy.
6.Start of the fertile phase – pre-ovulatory infertility
Infertility at the start of the cycle is relative – there is always a small risk of early ovulation. It may only be determined if the previous bleeding was a true menstruation, i.e. a temperature rise was confirmed in the previous cycle. Several rules are applied in parallel and the one indicating the earliest day applies. In addition, any sign of fertility (mucus, a feeling of wetness, the so-called sign of careful observation, a change in the cervix) ends the infertile phase immediately.
For beginners
Rötzer’s 6-day rule
The first 6 days of the cycle are considered infertile if there was no cycle shorter than 26 days in the past year.
Shortest cycle − 20
If cycles shorter than 26 days occurred: number of infertile days = length of the shortest cycle minus 20 (e.g. 25 − 20 = 5).
For experienced users (at least 12 cycles with temperature charting)
Modified Döring rule
The earliest day of the first higher temperature on record minus 7 (minus 6 if the rise occurred on day 13 or earlier). The margin corresponds to about 6 days of sperm survival plus a safety day.
Shortest cycle − 20
Based on the shortest of the last 12 cycles.
Last dry day
Infertile until the day before the first feeling of wetness or the so-called sign of careful observation (a characteristic sensation just before mucus appears). For users who know their signs very well.
Cervix
Until the last day of a low, firm and closed cervix.
A note on discrepancies: secondary sources differ in the details of these rules – e.g. some related methods (Sensiplan) allow beginners 5 instead of 6 days and use a “minus 8” instead of a “minus 7” rule. The applicable values should be taken from Prof. Rötzer’s handbook or from an INER teacher.
7.Effectiveness
The effectiveness of family planning methods is expressed by the Pearl Index (PI) – the number of unintended pregnancies per 100 women using the method for one year (about 1,300 cycles). Method effectiveness (perfect use) must be distinguished from user effectiveness (typical use, including mistakes and deliberate departures from the rules).
| Phase / rule | Pearl Index | Data source |
|---|---|---|
| Post-ovulatory phase (after confirmation) | 0 – no pregnancies in over 200,000 cycles | data collected by J. Rötzer[4] |
| First 6 days of the cycle | < 0.2 – 1 pregnancy in 8,532 cycles | Rötzer 1978[2] |
| Extended pre-ovulatory phase (until the first sign) | approx. 0.8–0.9 | J. Rötzer’s data[2, 4] |
| Overall user effectiveness in Rötzer’s study | 0.8 – 12 pregnancies in 17,026 cycles | Rötzer 1978[2] |
| Sympto-thermal method (international study), when following instructions | 0.93 (overall 7.47) | Rice et al. 1981[9] |
| Related sympto-thermal method (Sensiplan), perfect / typical use | 0.6 / 1.8 per 100 women over 13 cycles | Frank-Herrmann et al. 2007[6] |
A systematic review of 53 studies of fertility awareness-based methods (Peragallo Urrutia et al., 2018) found that sympto-thermal methods achieve the lowest pregnancy rates with perfect use, but the quality of the available studies is low to moderate and typical-use results vary widely.[8]
Critical appraisal: the most detailed figures for the Rötzer variant come from data collected by the method’s author and his collaborators. Independent prospective studies comparable to the Frank-Herrmann et al. cohort are lacking. In studies of sympto-thermal methods most unintended pregnancies result from deliberate intercourse in the fertile phase rather than from failure of the rules.
8.Scientific research
Extended temperature measurement
Rötzer describes basal temperature measurement supplemented by mucus observation and reports effectiveness comparable to ovulation inhibitors.[1]
Ten years of change
An analysis of over 17,000 cycles – effectiveness of the individual phases and rules of the method.[2]
A cohort of 900 women
A prospective study of a sympto-thermal method (17,638 cycles): 0.6 pregnancies per 100 women with perfect use.[6]
Couple relationships and satisfaction
A survey of 2,560 Rötzer method users from the USA and 7 European countries: 95% of women report knowing their body better, 65% of women and 74% of men a stronger relationship, fewer than 10% a negative effect.[7]
The fertile window
Conception is possible in a 6-day window ending on the day of ovulation – the basis for pre-ovulatory rules.[10]
Systematic review
53 studies of fertility awareness-based methods – higher-quality research is needed.[8]
9.Comparison with other methods
| Method | Indicators | Characteristics |
|---|---|---|
| Rötzer (NER) | temperature + mucus (+ cervix) | temperature evaluated only after the mucus peak; 6-day rule; Döring −7; reading takes about 5 min |
| Sensiplan (Germany) | temperature + mucus or cervix | double check without a required order; 5 days for beginners; “minus 8” rule; reading takes about 3 min |
| Billings | mucus only | rules based solely on mucus sensation and appearance |
| Temperature method | temperature only | infertility only after a confirmed temperature rise |
| Calendar (Ogino-Knaus) | cycle lengths | low effectiveness, ignores the variability of the current cycle |
10.Limitations and safety
- Requires learning (usually a few cycles), daily consistency and cooperation of both partners.
- Results can be disturbed by illness, medication, shift work, alcohol, travel and short sleep.
- Special situations – postpartum and breastfeeding, coming off hormonal contraception, perimenopause, anovulatory cycles – have separate rules that should be learned with a teacher.
- The method does not protect against sexually transmitted infections.
- Pre-ovulatory infertility is always relative; couples for whom avoiding pregnancy is particularly important may restrict themselves to the post-ovulatory phase.
How Rotzer uses this: the app records observations, draws the cycle chart and estimates cycle phases from them. When data are missing or rules conflict, it always chooses the more conservative option. The result is support, not an oracle – the final interpretation belongs to users who know the method.
11.Frequently asked questions
What is the Rötzer method?
It is a sympto-thermal method of fertility awareness developed by the Austrian physician Prof. Josef Rötzer. It combines daily basal body temperature readings with observation of cervical mucus, and evaluates the temperature only in relation to the mucus peak (double check).
When does post-ovulatory infertility begin in the Rötzer method?
On the evening of the day on which, after the mucus peak, the third consecutive higher temperature occurred – higher than the six preceding lower readings – with the third one at least 0.2 °C above the baseline. If the third does not reach 0.2 °C, a fourth higher temperature is awaited.
What is the mucus peak day?
The last day on which good-quality mucus was observed (e.g. like raw egg white, glassy, liquid, wet and slippery) before it deteriorated or disappeared. The peak is identified retrospectively, on the following day.
How many days at the start of the cycle are considered infertile?
For beginners, usually the first 6 days of the cycle if there were no cycles shorter than 26 days in the past year; otherwise the shortest cycle minus 20. Experienced users (at least 12 charted cycles) apply, among others, the modified Döring rule. Any earlier sign of fertility ends this phase. This is relative infertility.
How effective is the Rötzer method?
Data collected by Prof. Rötzer indicate a Pearl Index of 0 in the post-ovulatory phase, about 0.2 for the first six days of the cycle and about 0.8–0.9 when the pre-ovulatory infertile phase is extended. Typical-use effectiveness depends on proper instruction and adherence to the rules.
Can the Rötzer method be self-taught?
Sources recommend learning from a qualified teacher (e.g. INER – Institut für Natürliche Empfängnisregelung). Learning the basics usually takes a few cycles, and the rules for experienced users require at least 12 charted cycles.
12.References
- Rötzer J. Erweiterte Basaltemperaturmessung und Empfängnisregelung. Archiv für Gynäkologie. 1968;206:195–214. doi:10.1007/BF00666923.
- Rötzer J. The Sympto-Thermal Method: Ten Years of Change. The Linacre Quarterly. 1978;45(4).
- Rötzer J. Kinderzahl und Liebesehe. Wien: Herder; 1965.
- Rötzer J. Natürliche Empfängnisregelung. Der partnerschaftliche Weg – Die sympto-thermale Methode. 30th ed. Freiburg: Herder; 2006. Polish ed.: Naturalna regulacja poczęć. Droga współodpowiedzialności. Poznań: Święty Wojciech.
- Rötzer J. Der persönliche Zyklus der Frau. Von der Vorpubertät bis in die Wechseljahre. 1999.
- Frank-Herrmann P, Heil J, Gnoth C, Toledo E, Baur S, Pyper C, Jenetzky E, Strowitzki T, Freundl G. The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple’s sexual behaviour during the fertile time: a prospective longitudinal study. Human Reproduction. 2007;22(5):1310–1319. doi:10.1093/humrep/dem003.
- Unseld M, Rötzer E, Weigl R, Masel EK, Manhart MD. Use of Natural Family Planning (NFP) and Its Effect on Couple Relationships and Sexual Satisfaction: A Multi-Country Survey of NFP Users from US and Europe. Frontiers in Public Health. 2017;5:42. doi:10.3389/fpubh.2017.00042.
- Peragallo Urrutia R, Polis CB, Jensen ET, Greene ME, Kennedy E, Stanford JB. Effectiveness of Fertility Awareness–Based Methods for Pregnancy Prevention: A Systematic Review. Obstetrics & Gynecology. 2018;132(3):591–604. doi:10.1097/AOG.0000000000002784.
- Rice FJ, Lanctot CA, Garcia-Devesa C. Effectiveness of the sympto-thermal method of natural family planning: an international study. International Journal of Fertility. 1981;26(3):222–230.
- Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby. New England Journal of Medicine. 1995;333(23):1517–1521. doi:10.1056/NEJM199512073332301.
- Odeblad E. The discovery of different types of cervical mucus and the Billings Ovulation Method. Bulletin of the Natural Family Planning Council of Victoria. 1994;21(3):3–35.
- Barton M, Wiesner BP. Waking temperature in relation to female fecundity. The Lancet. 1945;246(6377):663–668.
Further reading: Institut für Natürliche Empfängnisregelung (iner.org), Instytut Naturalnego Planowania Rodziny, Poland (iner.pl).