Pregnancy Due Date & Ovulation Calculator (South Africa)

A pregnancy due date calculator estimates your expected date of delivery (EDD) using Naegele's Rule: the first day of your last menstrual period (LMP) plus 280 days, or 40 weeks. This is the same standard method used across South African maternity care — public and private alike — and aligns with the National Department of Health's Integrated Maternal and Perinatal Care Guidelines. If you know your conception date instead of your LMP, the equivalent estimate is conception date plus 266 days.

The LMP method assumes a 28-day cycle with ovulation on day 14. If your cycle runs longer or shorter than 28 days, the calculator adjusts the estimate accordingly — a 32-day cycle, for example, shifts ovulation (and your due date) about four days later than the standard calculation would suggest. This matters because the biggest source of error in LMP-based dating isn't the formula, it's an inaccurate or forgotten LMP date, or a genuinely irregular cycle. Where there's doubt, an ultrasound dating scan — ideally done in the first trimester — is more reliable than any calculator, LMP-based or otherwise.

Understanding your fertile window

For the same cycle, ovulation typically occurs around day 14 before your next expected period (calculated here as LMP date plus your cycle length, minus 14 days). Because sperm can survive in the reproductive tract for up to five days while the egg is viable for roughly 24 hours after ovulation, the fertile window usually spans about five days before ovulation through one day after it. This is the same logic clinics like Mediclinic and Marie Stopes SA use for their own fertility calculators.

Trimester dates and antenatal milestones

Pregnancy is conventionally divided into three trimesters: the first runs from your LMP to 12 weeks, the second from 12 to roughly 27-28 weeks, and the third from there to your due date. Two screening windows are worth flagging on your calendar early: the nuchal translucency (NT) scan, done between 11 weeks and 13 weeks 6 days, and the mid-pregnancy anatomy scan, typically booked between 18 and 22 weeks. Both are standard offerings through South African antenatal care, whether you're attending a public clinic, a midwife obstetric unit (MOU), or a private obstetrician.

BCEA maternity leave: what the law actually gives you

Under South Africa's Basic Conditions of Employment Act (BCEA), every employee is entitled to four consecutive months of maternity leave. That leave may start any time from four weeks before your expected date of birth — or earlier, if a medical practitioner or midwife certifies it's necessary for your health or your unborn child's health. After the birth, you may not return to work for six weeks unless a medical practitioner or midwife certifies you're fit to do so. None of this is means-tested or dependent on your employer's internal policy — it's a statutory minimum that applies regardless of company size or sector.

Maternity leave itself is typically unpaid by the employer under the BCEA (unless your contract or a bargaining council agreement says otherwise), but the Unemployment Insurance Fund (UIF) pays a maternity benefit to qualifying contributors during that period, calculated on a sliding scale up to roughly 66% of your average remuneration, subject to the UIF's own maximum threshold. The exact percentage and cap change periodically, so treat any online estimate — including this one — as illustrative only, and confirm your actual benefit amount by applying through labour.gov.za or your nearest Department of Employment and Labour office.

What this calculator does and doesn't tell you

This tool gives you three linked pieces of planning information from a single date: your estimated due date and gestational age, your fertile window for the cycle you entered, and a suggested BCEA leave window built backward and forward from your EDD. It does not diagnose, confirm viability, or replace an ultrasound — due dates calculated from LMP alone carry a margin of error that a dating scan narrows considerably, particularly if your cycles are irregular or you're unsure of your LMP date. Only around 5% of babies are born exactly on their calculated due date; anywhere from 37 to 42 weeks is considered a normal, full-term range.

If your pregnancy runs past 42 weeks by this estimate, or you experience danger signs — severe headache, blurred vision, heavy bleeding, reduced fetal movement, or severe abdominal pain — contact your healthcare provider immediately rather than relying on any calculator.